Sprinkler systems for turf irrigation are well known. Typical systems include a plurality of valves and sprinkler heads in fluid communication with a water source, and a centralized controller connected to the water valves. At appropriate times the controller opens the normally closed valves to allow water to flow from the water source to the sprinkler heads. Water then issues from the sprinkler heads in predetermined fashion.
There are many different types of sprinkler heads, including above-the-ground heads and “pop-up” heads. Pop-up sprinklers, though generally more complicated and expensive than other types of sprinklers, are thought to be superior. There are several reasons for this. For example, a pop-up sprinkler's nozzle opening is typically covered when the sprinkler is not in use and is therefore less likely to be partially or completely plugged by debris or insects. Also, when not being used, a pop-up sprinkler is entirely below the surface and out of the way.
The typical pop-up sprinkler head includes a stationary body and a “riser” which extends vertically upward, or “pops up,” when water is allowed to flow to the sprinkler. The riser is in the nature of a hollow tube which supports a nozzle at its upper end. When the normally-closed valve associated with a sprinkler opens to allow water to flow to the sprinkler, two things happen: (i) water pressure pushes against the riser to move it from its retracted to its fully extended position, and (ii) water flows axially upward through the riser, and the nozzle receives the axial flow from the riser and turns it radially to create a radial stream. A spring or other type of resilient element is interposed between the body and the riser to continuously urge the riser toward its retracted, subsurface, position, so that when water pressure is removed the riser will immediately proceed from its extended to its retracted position.
The riser of a pop-up or above-the-ground sprinkler head can remain rotationally stationary or can include a portion that rotates in continuous or oscillatory fashion to water a circular or partly circular area, respectively. More specifically, the riser of the typical rotary sprinkler includes a first portion, which does not rotate, and a second portion, which rotates relative to the first (non-rotating) portion.
The rotating portion of a rotary sprinkler riser typically carries a nozzle at its uppermost end. The nozzle throws at least one water stream outwardly to one side of the nozzle assembly. As the nozzle assembly rotates, the water stream travels or sweeps over the ground.
The non-rotating portion of a rotary sprinkler riser typically includes a drive mechanism for rotating the nozzle. The drive mechanism generally includes a turbine and a transmission. The turbine is usually made with a series of angular vanes on a central rotating shaft that is actuated by a flow of fluid subject to pressure. The transmission consists of a reduction gear train that converts rotation of the turbine to rotation of the nozzle assembly at a speed slower than the speed of rotation of the turbine.
During use, as the initial inrush and pressurization of water enters the riser, it strikes against the vanes of the turbine causing rotation of the turbine and, in particular, the turbine shaft. Rotation of the turbine shaft, which extends into the drive housing, drives the reduction gear train that causes rotation of an output shaft located at the other end of the drive housing. Because the output shaft is attached to the nozzle assembly, the nozzle assembly is thereby rotated, but at a reduced speed that is determined by the amount of the reduction provided by the reduction gear train.
With such sprinkler systems, a wide variation in fluid flow out of the nozzle can be obtained. If the system is subject to an increase in fluid flow rate through the riser, the speed of nozzle rotation increases proportionally due to the increased water velocity directed at the vanes of the turbine. In general, increases or decreases in nozzle speed can adversely affect the desired water distribution.
In addition to nozzle rotation and fluid flow variations, conventional rotary sprinkler systems often produce uneven water distributions. The rotating portion of a rotary sprinkler riser typically carries a nozzle at its uppermost end. The nozzle throws at least one water stream outwardly to one side of the nozzle assembly. As the nozzle assembly rotates, the water stream travels or sweeps over the ground, water is thrown in a coherent stream at some trajectory relative to the surface to be watered, the stream will tend to water a doughnut shaped ring around the sprinkler with little water being deposited close to the sprinkler. This is obviously a disadvantage since the vegetation close to the sprinkler will be under-watered.
Prior art rotary sprinkler systems are typically provided with some type of arc adjusting mechanism, often comprising two arc limit stops that are relatively adjustable to one another. Such stops are typically carried adjacent to one another with the stops being continuously coupled to a part of the drive reversing mechanism. In adjusting one stop relative to another, the adjustable stop(s) are often necessarily ratcheted over serrations or detents, thus making adjustment somewhat difficult or unnatural.
Rotary sprinklers having rotary drives often include some type of clutch that allows the rotary nozzle assembly to be forced past the drive without damaging the drive. Some such clutches comprise detent or serration type clutches as well as simple friction clutches. It would be desirable to have a clutch that acts like a friction clutch in terms of smoothness of operation but operates with minimal drag or torque. In view of the above, there is a need for an improved rotary sprinkler system for both above-the ground and pop-up rotary sprinkler systems. In particular, it is desirable that the rotary sprinkler system provides a consistent and predictable watering pattern and volume. In addition, the rotary sprinkler system should also be configured to prevent excessive wear on the rotating parts of the system. Furthermore, it is desirable that the rotary sprinkler system controls the rate of rotation of the nozzle. More particularly, it is desirable that the rotary sprinkler system keeps the rate of nozzle rotation relatively constant.